True, but once they're properly on target the Order can do that kind of damage in a very short amount of time, and that's the position they're in now. Belkar and Roy in particular are getting full attacks, Durkon has always been noted to be unusually proficient as a combatant for a cleric, Bloodfeast is fully online, all the grappling is letting Haley (and Serini, who has now actually fired a bolt) get sneak attacks if I remember the grapple rules, V is back in the fight and now at minimal risk, and all of this is after the 8 or more combat rounds this has already lasted(8 breath weapons: 1d4 recharge, it's been at least 8 rounds with an average of about 20).
Plus, I'm thinking the Paladins are likely to arrive with Sunny back online, which won't help Calder.
That said, I remain by my prediction that simply damaging Calder to death is not how this fight ends. I'm still expecting him to flee, and indirectly help Team Evil somehow as a result.